It is known that systems for room air-conditioning, typically in rooms of small and large buildings, essentially consist of a series of terminal devices (fan-coils or fan coil units), intended to perform the heat exchange with environment air, which are supplied with cold water (in summertime) or hot water (in wintertime) produced by centralised systems (refrigeration units, heat generators, or the like).
When building from scratch, these systems are fitted with water circulating networks specifically conceived for this function, hence coated with insulating and steam-barrier products, capable of preventing condensation from water vapour on the outer surface thereof. This coating, in addition to evident reasons of dissipation reduction, is essential and indispensable in order to:                prevent the water produced by said condensation water vapour phenomena from causing seepage and damages to the surrounding building structures,        safeguard duration in time of the metal pipes, minimising the corrosion effects induced by rust formation.        
Moreover, not less important but of more accessible solution, systems suitable for summer air-conditioning also have an integrative pipe system intended for the disposal of the condensation water which collects on the cold surfaces of the heat exchangers of the terminal units.
By contrast, for what concern the majority of existing buildings, intended for human occupation (residential housing, offices, schools, etc.), the relative water systems for fluid distribution are designed solely for transporting heating fluid; due to aesthetic requirements, fluid transport pipes are typically embedded in the walls, hence hardly reachable unless demolition actions are taken.
These water systems for conventional heating typically do not meet the above-described insulation and water vapour barrier requirements, and are hence unsuitable for being converted to the transfer of cooling fluid for the summer conditioning regimens. For such reason, should one not want to provide to the reconstruction of the original systems or to the installation of parallel air-conditioning systems—an often unacceptable choice due to the nuisance caused and to the particularly high costs involved—it is not possible to install a centralised air-conditioning system, but it is necessary to accept the compromise of installing a certain number of individual independent units (air-conditioning split or multi-split units fitted with external air condensation units, with water coolers where condensation is obtained through cool disposable drinking water, etc.).
Also, these independent units comprise evident disadvantages, since they generally have:                significant purchase and installation costs,        remarkable running costs, both in terms of energy efficiency and of maintenance requirements;        an increase of electric load distributed on the electric systems of the estate units,        a possible external functional impact, determined by hot air discharge towards the surrounding areas, as well as        an objective visual environmental impact detrimental to the external architectonic appearance of the building.        
It would instead be desirable to be able to develop a centralised system, so as to avoid the drawbacks linked to the independent units, which, however, reduces as far as possible the need for actions on the existing fluid circulating network of the building.
GB2247072 discloses an air-conditioning system having a heating system equipped with a distribution pipeline of a primary heat-exchange fluid between a central unit and a plurality of peripheral units for heat exchange with the environment air. This system however relies on a specific distribution pipeline and cannot be adapted to a pre-existing traditional circulating network for heating fluid.